1. Field of the Invention
The present invention relates to a spindle device of a machine tool, and more particularly, to a spindle device capable of having improved efficiency in collecting cutting chips in dust form generated especially during the machining of light metal.
2. Description of the Related Art
As a milling cutter in which cutting chips in dust form generated during a cutting process of, for example, a magnesium alloy can be collected, there is one described in Japanese Patent Application Publication No. 2005-532917. This milling cutter has a suction opening formed in an axial core of a shank, and the suction opening communicates with a suction hopper attached to a clamping and supplying device.
The aforesaid conventional milling cutter has a problem that the structure is complicated since the suction hopper is attached to the clamping and supplying device, and automatic tool change is not possible due to a structural reason.
Here, as a spindle device capable of solving the above problems, the present applicant has developed a spindle device in which a suction hole extending from a tool holder to penetrate through a draw bar in a spindle is formed and cutting chips are sucked from the suction hole. The structure having the suction hole may cause a problem of increasing the outside diameter of the draw bar, and as a result, increasing the inside diameter of the spindle compared with that in the conventional art, depending on the structure of the draw bar, and further, may lower suction efficiency because air is sucked from a portion connected to a drive mechanism reciprocatingly driving the draw bar.